Abstract: Isocyanates are prepared by a process in which a product stream from the isocyanate synthesis is purified.

Abstract: A process is described for preparing diaminodiarylmethanes comprising the steps a) reacting an aromatic amine with a methylene-donating agent in the presence of homogeneous acid catalysts, b) removing the homogeneous acid catalyst from the reaction product, c) working up and purifying the reaction product, which comprises removing the homogeneous acid catalyst from the reaction mixture by adsorption to a solid adsorbent.

Abstract: The invention relates to a process for preparing chlorine by catalytic gas-phase oxidation of hydrogen chloride, which comprises the steps: a) providing a feed gas stream I comprising hydrogen chloride and a feed gas stream II comprising oxygen; b) in a first oxidation stage, feeding the feed gas stream I, the feed gas stream II, if desired a recycle stream la comprising hydrogen chloride and if desired an oxygen-containing recycle stream IIa into a first oxidation zone and bringing them into contact with a first oxidation catalyst so that a first partial amount of the hydrogen chloride is oxidized to chlorine and a gas stream III comprising chlorine, unreacted oxygen, unreacted hydrogen chloride and water vapor is obtained; c) in a second oxidation stage, feeding the gas stream III into a second oxidation zone and bringing it into contact with at least one further oxidation catalyst so that a second partial amount of the hydrogen chloride is oxidized to chlorine and a product gas stream IV comprising chlorin

Abstract: The invention relates to a process for preparing polyisocyanates by reacting organic amines with phosgene, wherein the reaction is carried out in at least three stages, with the first stage being carried out in a mixing apparatus, the second stage in at least one residence apparatus and the third stage in at least one separation apparatus and the pressure in each successive stage being lower than that in the previous stage.

Abstract: The invention relates to a process for preparing polyisocyanates by reacting primary amines with phosgene, which comprises the steps a) mixing the amine with the phosgene, b) reacting the amine with the phosgene in a residence reactor and, if desired, c) transferring the output from the reactor of step b) into a distillation column, wherein the residence reactor in step b) is configured as a tube reactor.

Abstract: The present invention relates to a continuous process for preparing isocyanates by reacting primary amines with phosgene, wherein the reaction is carried out in a cascade of at least two tube reactors and the gas phase formed in the reaction is separated off in a phase separator after each reactor and only the liquid phase is passed to the next reactor or to product purification and the reaction volume of the first tube reactor is only a fraction of the total reaction volume.

Abstract: Process for preparing high-concentration formaldehyde solutions having a CH2O content of ?50% by weight from an aqueous formaldehyde solution having a lower CH2O content by evaporation of part of this solution (partial evaporation), in which the aqueous formaldehyde solution is heated to an evaporation temperature T at which the gas phase becomes enriched in water relative to the liquid phase and the gas phase formed is taken off continuously or discontinuously, wherein the evaporation temperature T obeys the relationship: T[° C.]<Tmax[° C.] where Tmax(c)=A+B×(c/100)+C×(c/100)2+D×(c/100)3 and A=+68.759, B=+124.77, C=?12.851, D=?10.095, where c is the instantaneous CH2O content of the aqueous formaldehyde solution during the evaporation in percent by weight and is from 20 to 99% by weight.

Abstract: The invention relates to starting compounds which can be used for the preparation of polyurethanes and can be prepared by reaction of hydroxyl-containing oligomers of formaldehyde.

Abstract: Process for preparing high-concentration gaseous formaldehyde having a molar CH2O:H2O ratio of ?0.6 from an aqueous formaldehyde solution by evaporation of at least part of the solution, in which the aqueous formaldehyde solution is heated to a vaporization temperature T and the gas phase formed is taken off, wherein the evaporation temperature T obeys the relationship: T[° C.]?T?min[° C.] where T?min(c)=A+B×(c/100)+C×(c/100)2+D×(c/100)3 and A=+68.759, B=+124.77, C=?12.851, D=?10.095, where c is the instantaneous CH2O content of the aqueous formaldehyde solution during the evaporation in percent by weight and is from 20 to 99% by weight.

Abstract: The present invention relates to a process for preparing alkyl thiols by adding hydrogen sulfide to double bonds of C6-C20 olefins at a temperature of from 20 to 150° C. and a pressure of from 1 to 40 bar, wherein the reaction is carried out in the presence of at least one organic, liquid acid, and to the use of organic, liquid acids as a catalyst for increasing the selectivity and/or reaction rate in the addition of hydrogen sulfide to double bonds of C6-C20 olefins to prepare alkyl thiols.

Abstract: The invention relates to a method for producing isocyanates by reacting primary amines with phosgene in the gaseous phase. Said method is characterized in that the reaction of amine and phosgene occurs in a reaction channel, the internal dimensions of which have a width/height ratio of at least 2/1.

Abstract: The invention relates to a catalyst for the catalytic oxidation of hydrogen chloride, comprising on a support a) from 0.001 to 30% by weight of gold, b) from 0 to 3% by weight of one or more alkaline earth metals, c) from 0 to 3% by weight of one or more alkali metals, d) from 0 to 10% by weight of one or more rare earth metals, e) from 0 to 10% by weight of one or more further metals selected from the group consisting of ruthenium, palladium, platinum, osmium, iridium, silver, copper and rhenium, in each case based on the total weight of the catalyst.

Abstract: Isocyanates are prepared by a process in which a product stream from the isocyanate synthesis is purified.

Abstract: The invention relates to a process for the partial or complete separation of a mixture comprising hydrogen chloride and phosgene, possibly solvents and possibly low boilers and inerts as are typically obtained in the preparation of isocyanates by reaction of amines with phosgene, which comprises firstly carrying out a partial or complete condensation of phosgene, then a distillation or stripping step in a column to remove the hydrogen chloride from the bottom product phosgene and subsequently a scrub of the top product hydrogen chloride by means of the process solvent to absorb the phosgene in the process solvent. An after-purification by means of adsorption on activated carbon or by another suitable method can subsequently be carried out to remove solvent residues.

Abstract: The present invention relates to a process for preparing sulfur-containing compounds of the general formula I in which Q, R1 and R2 are each independently defined as follows: Q: —S— or —S—S—, R1: hydrogen or saturated or unsaturated, linear or branched C1-C30-alkyl radical, R2: hydrogen or saturated or unsaturated, linear or branched C1-C30-alkyl radical, where R1 and R2 are not simultaneously hydrogen, by reacting a mixed gas stream comprising hydrogen sulfide, with or without oxygen, with linear or branched C1-C30-olefins, which comprises carrying out the reaction in the presence of water and carbon dioxide at a pressure of from 2 to 325 bar.

Abstract: The invention provides a process for preparing isocyanates by reacting amines with phosgene, wherein the phosgene-containing feed stream has a hydrogen chloride content of more than 0.8% by mass.

Abstract: Process for preparing chlorine from hydrochloric acid, which comprises the steps: a) providing a hydrochloric acid feed stream I; b) providing a hydrochloric acid recycle stream II; c) separating off a hydrogen chloride stream IV from the hydrochloric acid feed stream I and the hydrochloric acid recycle stream II in a distillation step; d) feeding the hydrogen chloride stream IV, an oxygen-containing steam V and, if desired, an oxygen-containing recycle stream Va into an oxidation zone and oxidizing hydrogen chloride to chlorine in the presence of a catalyst to give a product gas stream VI comprising chlorine, unreacted oxygen, unreacted hydrogen chloride and water vapor; e) separating off hydrogen chloride and water from the product gas stream VI in an absorption step to give a gas stream VII and the hydrochloric acid recycle stream II; f) if desired, drying the gas stream VII; g) separating off an oxygen-containing stream from the gas stream VII and, if desired, recirculating at least part of this as oxygen

Abstract: The present invention relates to a process for preparing isocyanates by reaction of amines with phosgene in a reactor and subsequent separation of the isocyanate from the reaction mixture leaving the reactor and purification of the isocyanate, wherein the separation and purification of the isocyanate is carried out in a column having a pressure at the top of 1-950 mbar, preferably 5-50 mbar, particularly preferably 10-20 mbar, and a temperature at the bottom of 90-250° C., preferably 120-170° C., particularly preferably 130-150° C., and the pure isocyanate stream is preferably taken off in liquid or gaseous form at a side offtake of the column.

Abstract: The invention relates to a process for preparing isocyanates by reaction of amines with phosgene in the presence of inert organic solvents in a reactor and subsequent work-up of the reaction mixture leaving the reactor, wherein the solvent is separated off in a two-stage or multistage, preferably two-stage, distillation process in which the solvent is separated off at a pressure of 0.1-15 bar in a first apparatus and at 1-900 mbar in a second apparatus or further apparatuses, with the heat of condensation of the solvent vapor from the first apparatus being used for partial or complete vaporization of solvent in the second apparatus.

Abstract: In a process for the preparation of isocyanates from carbamic esters, (i) a mixture containing a monofunctional or polyfunctional carbamic ester is passed continuously into a cleavage reactor or a cascade of two or more cleavage reactors, (ii) the carbamic ester is subjected to a thermal cleavage to give isocyanate and alcohol, (iii) the cleavage gas escaping from the cleavage reactor or reactors and containing the isocyanate, the alcohol, any uncleaved and/or partly cleaved carbamic ester and byproducts is brought into contact with a liquid coolant and condensing agent, cooled and at least partly condensed and (iv) the isocyanate and the alcohol are obtained from the cooled cleavage gas and the condensate in a rectification column, a part-stream of the alcohol obtained being used as liquid coolant and condensing agent for cooling and condensing the cleavage gas.